#include<iostream>
#include<vector>
#include<unordered_map>
using namespace std;
class Solution {
public:
    int singleNumber(vector<int>& nums) {
        unordered_map<int, int> hash;
        for (auto e : nums) {
            hash[e]++;
        }
        int n;
        for (auto& e : hash) {
            if (e.second == 1) {
                n = e.first;
                break;
            }
        }
        return n;
    }
};
int main()
{
	return 0;
}